Curing system for vinylpyridine rubbers



United States Patent "ice Henry E. Railsback, Bartlesville, Okla assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application August 2, 1956 Serial No; 601,632.

20 Claims. (Cl. 260-795) This invention relates to vinylpyridine rubbers and improved curing system for preventing premature vulcanization or scorch of vinylpyridine rubbers.

It is important in the. com unding of a rubber that vulcanizing ingredients be employed which are. efiective in curing the rubber in a reasonable time, which give a final product which has good physical properties and which enable therubber mass to be processed without premature vulcanization or scorch. Additives which produce desirable efiects in some ways can have deleterio'us, effects in others. In general, .the vulcanization ingredients must be carefully selected for the particular rubber which is to be processed in order that the desired :results will be attained. One of the problems which is sometimes. encountered in the preparation of rubbers is the problem of premature vulcanization or scorch. When a rubber has been compounded with the necessary additives, it is necessary that the rubber mass remain in an unvulcanized state during the milling, storing and other processing steps which take place prior to vulcanization. It is desirable, in other words, that the rubber does not vulcanize or assume a non-plastic state. for a sufficiently long period of time to allow proper milling, molding, or working of the rubber; Premature vulcanization changes the properties of the rubber product and renders it worthless for manyuses. Thus, rubber masses which have an undesirably marked tendency to vulcanize prematurely are said to have a high scorch tendency or a low scorch time;

It is known that synthetic rubbers obtained by the copolymerization ofvinylpyridines with conjugated dienes and the copolymerization of vinylpyridines with conjugated dienes and other copolymerizable materials when compounded and cured havemany desirable characteristics but have the disadvantage of exhibiting a tendency to scorch in a very short time as compared to other types of synthetic rubber compounds. The tendency of vinylpyridine rubbers to scorch is one of the most serious problems connected with the use of these materials. Failure in the prior art to provide a solution for the scorch problemhas hindered to some extent theme of this type of synthetic rubberby the industry.

It is an. object. of this invention to provide improved vinylpyridine rubbers. v

Another object of this invention is to provide improved rubber masses which can be cured without scorch or premature vulcanization.

Still another object of this invention is to prevent premature vulcanization or scorching during the curing of vinylpyridine rubbers.

. Yet another ObjOCtyOf, this invention is to provide an improved process for curing vinylpyridine rubbers.

2,927,099 Patented Mar. 1, 1960 According to this invention, in one aspect thereof, there is provided an improved vulcanizing or curing system comprising sulphur, 4-4-dithiodimorpholine and a material, selected from the group consisting of N-oxydiethylene 2 benzothiazylsulfenamide and N-cyclohexyl-Z- benzothiazylsulfenamide.

In another aspect, the invention comprises improved vinylpyridine rubbers prepared by incorporating in said rubbers sulphur, 4-4-dithiodimorpholine and a compound selected from the group consisting of N-oxydiethylene-Z- benzothiazylsulfenamide and N-cyclohexyl-Z-benzothiazylsulfenamide.

In still another aspect, the invention comprises a method of curing a vinylpyridine rubber mix by incorporating therein a vulcanizing composition comprising sulphur, 4-4'-dithiodimorpholine and a compound selected from the group consisting of N-oxydiethylene-Z-benzothiazylsulfenamide and N-cyclohexyl-2-benzothiazylsulfenamide'and subjecting the rubber mix to suitable curing conditions.

The vinylpyridine polymers in which the accelerators of this invention are incorporated are rubbery copolymers of one or more conjugated dienes with one or more vinylpyridine compounds. The vinylpyridine compounds employed can be represented by the formula gen, alkyl, vinyl, and alpha-methylvinyl (isopropenyl) groups, with at least one and not more than two of the groups being vinyl or alpha-methylvinyl, and the total number of carbon atoms in the alkyl groups being not greater than 12. The alkyl groups are preferably methyl and ethyl groups. Examples of such materials are: 2-viny1pyridine, 3-vinylpyridine, 4-vinylpyridine, 2-vinyl- S-ethylpyridine, 2,5 -divi=nylpyridine, 2 methyl 5 vinylpyridine, 2,3,4-trimethyl-5-vinylpyridine, 3-ethyl-S-vinylpyridine, Z-methyl-S-isopropenylpyridine, 2,4-dimethyl- 5 -isopropeny1pyridine, 3 ethyl S isopropenylpyridine, 2-isopropenylpyridine, and 2-vinyl 3,5 diamylpyridine, and 2-vinyl-4,6-dihexylpyridine.

The conjugated dienes employed in the production of vinylpyridine copolymers are preferably those containing from 4 to 6 carbon atoms per molecule, e.g., 1,3-butadiene, isoprene, piperylene, methylpentadiene, 2,3-dimethyl- 1,3 -butadiene and chloroprene. Conjugated dienes having more than 6, e.g., 8, carbon atomsper molecule can, however, be used when desired. Alkoxy derivatives, such as methoxybutadiene, ethoxybutadiene, etc., cyano derivatives of conjugated dienes, such as Z-cyanobutadiene, 2-methyl-3-cyanobutadiene, and the like can also be used.

In addition to the preceding compositions, the vinylpyridine rubber can contain a third type of polymerizable memos monomer, for example, styrene or an alkoxy derivative thereof, such as methoxystyrene, ethoxystyrene; alkyl substituted styrenes, such as methylstyrene, ethylstyrene; acrylonitrile, methacrylonitrile; acrylates, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate; methacryla-tes such as methyl methacrylate and the like.

In the preparation of vinylpyridine rubbers, the proportion of the various monomers can vary over a wide range. For example, the conjugated diene can vary from 50 to 98 parts by weight, the vinylpyridine compound from 50 to 2 parts by weight and the third monomer, such as acrylonitrile, from to 48 parts by weight per 100 parts by weight of total monomers. The ranges given aremerely illustrative in nature and are not intended to'include all of the polymers which can be prepared by the use of various combinations of the monomers given.

The vulcanizing system of this invention comprises sulphur, 4-4'-dithiomcrpholine and a compound selected from the group consisting of N-oxydiethylene-Z-benzothiazylsulfenamide and N-cyclohexyl-Z-benzothiazylsulfenamide. It has been found that when these materials are present, vinylpyridine rubbers can be compounded without danger of scorching during milling and the resulting vulvanizates have excellent properties. The amount of sulphur employed in the vulcanization or curing System is between about 0.4 and about 2.25 parts by weight; the amount of 4-4 dithcdimorpholine is between about 0.5 and about 4 parts by weight and preferably between about 1.0 and about 2.5 and the amount of compound selected from the group consisting of N-oxydiethylene- 2-benzothiazylsulfenamide and N-cyclohexyl-Z-benzothiazylsulfenamide is between about 0.25 and about 2 parts by weight and preferably between about 0.5 and about 1.25, all per 100 parts of rubber. These materials are ordinarily incorporated into the rubber mass along with other additives such as fillers, softeners, etc. The components which make up the vulcanizing system can be introduced separately into the rubber mass or they can be admixed prior to being incorporated into the rubber.

The vinylpyridine copolymers are prepared according to methods well known in the art, for example, by mass or emulsion polymerization techniques utilizing suitable catalyst compositions. The polymers are then mixed with the desired additives and subjected to the usual milling or working treatments. The mass, thus obtained, is then subjected to molding and vulcanization as known in the art.

In general the polymerization process is carried out by forming an emulsion of the monomers in water with the aid of an emulsifying agent such as a fatty acid soap, a rosin acid soap, an alkyl aryl sulfonate, etc. Other ingrcdients include activators, initiators and modifiers. Preferably the system is maintained alkaline, that is, at a pH of about 9-l2 and the polymerization takes place at a temperature between about 40 F. and about 150 F. A large variety of polymerization recipes can be used, typical of which are the potassium persulfate recipe, the sodium formaldehyde sulfoxylate recipe and the ferrous pyrophosphate recipe.

The mass polymerization process is carried out in a nonaqueous system in the presence of a diluent material. Suitable diluents include acyclic hydrocarbons, such as n-butane, n-pentane, etc., alicyclic hydrocarbons, such as cyclohexane and aromatic hydrocarbons such as benzene. The catalyst employed is usually an alkali metal, such as sodium.

The following examples are presented in illustration of the various aspects of the invention:

EXAMPLE I Butadiene was copolymerized with 2-methyl-5-vinylpyridine in aqueous emulsion at 41 F. Five runs were made in accordance with the following recipes:

Parts by Weight Wate1. 200

0.10 75 25 6 0. 10 0. 40 Tamol N 0.30 FeSO .7H:O 0.02 0.02 Sequestrene AA 3 0. 0t 0. 04 Sodium formaldehyde sulfoxylatc 0. 10 0. l0 Cumene hydroperoxido 0. 10 p-Menthane hydroperoxide; 0. 1O 'lert-dodecyl mercaptan, original charge. Var able Variable Tert-dodecyl mercaptan, booster 7 Variable Variable Shortstop: Thiostop N Antioxidant (parts by 100 parts rubber):

Phenyl-bsta-naphthylaniine.

1 Charged with mercaptan booster. 1 Sodium salt of a naphthalene sulionic acid condensed with formalde- 11 do.

317 Ethylene diemine tetraacetic acid.

4 Sodium dimethyldithiocarbamato.

M ercaptan increment Mer- Re- Conversion captan, Conaction Mooney Run No. Recipe Part Part version, Time, I

' Original Percent Hours Charge Percent Mil-4 A 0.21 0.21 60 34.0 88 04 a 0.22 0.22 r so 32.5 92 60 B U. 23 0. 23 62 20. 3 95 0* B 0. 26 0. 26 00 20. 9 90 g6 B 0. 23 0. 23 G0 15. 5 00 3 t4 1 One-half charge of activator and cumene hydroperoxide at 28.8 hours (84.4 percent conversion).

Two initiator boosters: Each one-halt charge of activator and cumene hydroperoxide added at 17.4 an 25.4 hours, respectively (60.0 and 84.3 percent conversions).

a Vented Mooney.

The latices were blended and the blend was coagulated. The brine-acid procedure was utilized for coagulation'with the crumb being given two caustic washes and two water washes (all at 150 The final product had a Mooney value (ML-4) of 55.

The butadiene/2-methyl-5-vinylpyridine rubber was compounded in accordance with thefollowing tread. recipe: 7 Parts by Weight 1 High abrasion furnace black.

Mixture of equal parts by weight of Circosol 'ZXH with Paraflux (Circo'sol 2XH: A petroleum hydrocarbon softener, containing hydrocarbons of high molecular weight, in the form of a heavy, viscous, transparent. Pale green, odorless liquid of low volatility; sp. gr. 0.940; Saybolt Universal viscosity at F., about 2,000 seconds. Para. Flux Z016: Saturated polymerized hydrocarbon). I

Physical mixture containing 65 percent of a complex diarylamineketone reaction product and 35 percent of N,N diphenyl-p-phenylenediamine.

4 4,4 -Dithiodimorpholine.

6 Noxydiethylene-2-benzothiazylsulfenamide.

in Tables 1 and 2.

'7 Two runs were made. Details are shown in the following table:

Soap Time, Conver- Mer- Mooney Run N 0. Solution, Hours on, captan, (M L4) pH Percent Parts Stripped l One-half charge of activator and cumene hydropcroxide added at 5.7 hours (1.5 percent conversion).

2 One-half in original charge and one-half at 59.5 percent conversion.

3 One-half in original charge and one-half at 60.9 percent conversion.

, The latices were blended and the blend was coagulated using the brine-acid technique. The crumb was given two -minute caustic washes at a temperature of 150 F. followed by two 15 minute hot water Washes. The final product had a Mooney value (ML4) of 56.

A butadiene/Z-methyl-5-vinylpyridine/acrylonitrile terpolymer was prepared by emulsion polymerization at 41 F. in accordance with the following recipe:

Parts by weight Water 200 Butadiene 70 2 methyl-S-vinylpyridine 10 Acrylonitrile Potassium fatty acid soap 6 KOH 0.1 KCl 0.3 Tamol N 1 0.3 F6804 Sequest-rene AA 1 0.04 Sodium formaldehyde sulfoXylate 0.1 p-Menthane hydroperoxide 0.1 tert-Dodecyl mercaptan Variable Shortstop: Goodrite 3955 0.15

Antioxidant (phr.): Phenyl beta naphthylamine 1 As in Example I.

Two runs were made. Details are shown in the following table:

Mer- Mcrcaptan Increment Conversion, captain, Re- Mooney Run No. Part action Original Time, Conver- Time,

Charge Part Hours sion, Hours Percent (M L-4) Percent Rubber 100 Carbon black (Philblack O) 1 50 Zinc oxide 3 Stearic acid 1 Circe-para 1 1O Flexamine Y 1 Sulfur Variable Sulfasan R 1 Variable NOBS vSpecial 1 Variable 1 As in Example I. The stocks were milled, bored minutes at 307 F.,

and physical properties determined. Results are given in Table 3.

TABLE 3 BD/Styrene/MVP BD/MVP/Acry- Sample No. lonitrile Sample No.

Unaged: v

Sulfur. phr 1 1. 75 1 1. 75 Sulfasan R, phr. 1. 5 1. 5 NOBS special, phr 0.75 1.0 0. 75- 1.0 Compression set, percent 15. 8 15. 4 16. 2 14. 2 300 Percent modulus,

p.s.i., C 1,630 1,375 2,000 1,990 Tensile, p.s.i., 80 F 2,880 2, 770 3, 170 3, 310 Elongation, perce 80 F 430 475 430 470 AT, F 60. 5 72.6 66. 6 74. 7 Resilience, percent 64. 8 61. 5 58. 9 59. 1 Flex life, thousands of flexures to failure 2. 7 3.0 6. 4 (i. 9 Shore hardness 57. 5 57. 5 64. 5 65. 5 212 F. compounded MS-Hfi 35. 5 36. 6 37. 5 39 Scorch at 280 F.:

Minimum Mooney. 37. 5 39. 5 37. 5 40 5 point rise, minutes- ,27 15. 5 14. 5 7. 5 Aged 24 hours at 212 F.:

300 percent modulus,

p.s.i., 80 F 2, 070 2, 010 2, 675 2, 750 Tensile, p.s.i., 80 F 2, 910 2,820 3, 340 3,160 Elongation, percent,

80 F 380 385 375 340 AT, "3 59. 1 67.6 63. 5 70. 3 Resilience, percent 66. 5 64. 3 61.8 61.2 Flex life, thousands of flexures to failure" 2.8 2. 2 18.8 8.8 Shore hardness 62.5 62 69 69.5

1 Butadienelstyrcne/z-methyl-5-vinylpyridine. 2 Butadiene/2-methyl-fi-vinylpyridine/acrylonitrile.

EXAMPLE III An /15 butadiene/2-methyl-5-vinylpyridine rubber was compounded in accordance with the following tread 1 As in Example I. 0 TABLE 4 The stock was milled, cured 30 minutes at 307 F., and physical properties determined. The results are given in Table 4.

Unaged:

Mooney value, ML-4 50.1 Compression set, percent 15.3 300 percent modulus, p.s.i., 80 F 1,780 Tensile, p.s.i., 80 F 3,030 Elongation, percent, 80F. 430 AT, F 60.8 Resilience, percent 62.2 Flex life, thousands of flexures to failure 5.0 Shore hardness 62 212 mpounded Ms 1 335 Scorch at 280 F Minimum Mooney 37 5 point rise, minutes 19.5 Oven aged 24 hours at 212 F.:

300 percent modulus, p.s.i., 80 F 2,130 Tensile, p.s.i., 80 F 2,970 Elongation, percent, 80 F. 360 AT, F. 57.5 Resilience, percent 66.4 Flex life, thousands of flexures to failure 3:5. Shore hardness 62.5

11 TABLE 7 Compression set, percent 17.0 300% modulus, p.s.i., 80 F. 1,580 Tensile, p.s.i., 80 F. 3,080 Elongation, percent, 80 F. 505 Shore hardness 60.5

Scorch at 280 F.:

Minimum Mooney 28 point rise, minutes 16.5

1 On compression set pellets.

The preceding examples illustrate the effectiveness of curing various vinylpyridine rubbers with vulcanizing systems containing sulfur, 4-4' dithiodimorpholine and N-oxydiethylene-2-benzothiazylsulfenamide and N-cyclohexyl-Z-benzothiazylsulfenamide. Referring particularly to Table I, which contains vulcanization data of a 75/25 butadiene-Z-methyl-5-vinylpyridine copolymer, it is to be noted that samples 26 and 27, which contained no sulfur, failed to cure. The same is true of samples 28 and 29 which contained less than 0.4 part of sulfur per 100 parts of rubber. Sample 25 which contained no 4-4 dithiodirnorpholine was cured, however, the scorch time at 280 F. (minutes to 5 point rise) was very low, indicating poor resistance to scorch. The effect of various quantities of 4-4 dithiodimorpholine is clearly shown by runs 2, 3, 4 and 5, where the quantity of sulfur and Noxydiethylene-Z-benzothiazylsulfenamide were held constant. 7

Referring to the data on scorch it is noted that as the amount of 4-4 dithiodimorpholine is increased from 1.0 to 2.5 parts, the scorch time at 280 F. (minutes to 5 point rise) increased from 14 to 22 minutes and the scorch time at 300 -F. (minutes to 5 point rise) increased from 8 to 12.5 minutes, thus indicating the eifectiveness of increased amounts of this material in the vulcanization system.

The data of this table and the other examples as presented in Tables 2 to 6 similarly illustrate the effectiveness of the vulcanization system of this invention. For example, in Table 3 are presented data relating to the vulcanization of terpolymers of butadiene, styrene and 2- methyl-S-vinylpyridine and butadiene, 2-methyl-5-vinylpyridine and acrylonitrile. It is to be noted that a substantial increase in scorch time (minutes to 5 point rise) is obtained with the use of the three component mixture sulfur, 4-4' dithiodimorpholine, N-oxydiethylene-Z-benzothiazylsulfenainide. Tables 4, 5 and 6 show the effectiveness of the aforedescribed vulcanizing mixture when used with a series of butadiene-Z-methyl-5-vinylpyridine copolymers in preventing premature vulcanization or scorch. In Table 7 similar data is presented for a 75/25 butadiene-2-methyl-5-vinylpyridine copolymer vulcanized with sulfur, 4-4' dithiodimorpholine and N-cyclohexyl-2-' benzothiazylsulfenamide, again illustrating the effectiveness of the 3-component mixture in preventing scorch.

I claim:

1. A vulcanized rubber. prepared by incorporating into a rubbery copolymer of butadiene and 2-methyl-5-vinylpyridine prepared from a monomer mixture containing from about 25 to about 5 parts of Z-methyl-S-vinylpyridine and from about 75 to about 95 parts butadiene, between about 0.4 and about 2.25 partsof sulfur, between about 0.5 and about 4 parts of 4,4 dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N-oxydiethylene-Z- benzothiazylsulfenarnide and N-cyclohexyl-Z-benzothiazylsulfenarnide, based on 100 parts of, rubber and vulcanizing the rubber.

2. The vulcanized rubber of claim 1 in which the compound is N-oxydiethylene-Z-benzothiazylsulfenamide.

3. The vulcanized rubber of claim 1 in which the compound is N-cyclohexyl-Z-benzothiazylsulfenamide.

4. A vulcanized rubber prepared by incorporating into a'terpolymer of styrene, butadiene, and 2-rnethyl-5-vinylpyridine, prepared from a monomer mixture containing from about 25 to about 5 parts by weight of 2-methyl-5- vinylpyridine, from about 75 to about 95 parts by weight of butadiene and up to about 45 parts by weight of styrene, between about 0.4 and about 2.25 parts of sulfur, between about 0.5 and about 4 parts of 4-4' dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N- oxydiethylene-Z-bnzothiazylsulfenamide' and N-cyclohexyl-Z-benzothiazylsulfenamide, based on 100 parts of rubber and vulcanizing the rubber.

5. The vulcanized rubber of claim 4 in which the compound is N-oxydiethylene-Z-benzothiazylsulfenamide.

6. The vulcanized rubber of claim 4 in which the compound is N-cyclohexyl-2-benzothiazylsulfenamide.

7. The method for curing a rubbery copolymer of butadiene and 2-methyl-5-vinylpyridine prepared from a monomer mixture containing from about 75 to about 95 parts by weight of butadiene and from about 25 to about 5 parts by weight of 2-methyl-5-vinylpyridine which comprises incorporating with said rubber between about 0.4 and about 2.25 parts of sulfur, between about 0.5 and about 4 parts of 4-4' dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N-oxydiethylene-Z-benzothiazylsulfenamide and N-cyclohexyl-Z-benzothiazylsulfenamide, based on 100 parts of rubber and vulcanizing the rubber.

8. The method for curing a rubbery terpolymer of butadiene, styrene and 2-methyl-5-vinylpyridine prepared from a monomer mixture containing from about 75 to about 95 parts by weight of butadiene, up to about 45 parts by weight of styrene and from about 25 to about 5 parts by weight of 2-methyl-5-vinylpyridine which comprises incorporating with said rubber between about 0.4 and about'2.25 parts of sulfur, between about 0.5 and about 4 parts of 4-4' dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N-oxydiethylene-Z-benzothiazylsulfenamide and N-cyclohexyl-Z-benzothiazylsulfenamide, based on 100 parts-of rubber and vnlcanizing the rubber.

9. A vulcanized rubber prepared by incorporating into a rubber selected from the group consisting of rubbery copolymers of vinylpyridines represented by the formula R R N where R is selected from the group consisting of hydrogen, alkyl, vinyl and alpha-methyl vinyl groups, with at least one and not more than two of the groups being selected from the group consisting of vinyl and alphamethylvinyl, and the total number of carbon atoms in the alkyl groups being not greater than 12, with conjugated dienes containing 4 to 8 carbon atoms per molecule and cyano and lower alkoxy substituted conjugated dienes; and rubbery terpolymers of said vinylpyridines with (1) said conjugated dienes and cyano and. lower alkoxy substituted conjugated dienes and (2) 'polymerizable monomers selected from the group consisting of styrene, lower alkyl and alkoxy substituted styrenes, acrylonitrile, methacrylonitrile and lower alkyl acrylates and methacrylates; in which the monomer mixture from which the copolymers and terpolymers are prepared contains from about 25 to about 5 parts by weight of the vinylpyridine, from about 75 to about parts by weight of the conjugated diene and cyano and lower alkoxy substituted conjugated dienes and from 0 to about 45 parts by weight of the polymerizable monomer; between about 0.4 and about 2.25 parts of sulfur, between about 0.05 and about 4 parts of 4-4 dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group meannes- 13 consisting of N-oxydiethylene-2 benzothiazylsnlfenamide and N-cyclohexyl-Zbenzotliiazylsulfenamide, based on 100 par-ts of said rubber and vulcanizing the rubber.

10. A composition of matter comprising a rubber selected from the group consisting of rubbery copolymers of vinylpyridines represented by the formula cule and cyano and lower alkoxy substituted conjugated dienes; and rubbery terpolymers of said vinylpyridines with (1) said conjugated dienes and cyano and lower all;- oxy substituted conjugated dienes and (2) polymerizable monomers selected from the group consisting of styrene, lower alkyl and alkoxy substituted styrenes, acrylonitrile,

methacrylonitrile and lower alkyl acrylatm and methacrylates; in which the monomer mixture from which the copolymers and terpolymers are prepared contains from about 25 to about 5 parts by weight of the vinylpyridine, from about 75 to about 95 parts by weight of the conjugated diene and cyano and lower alkoxy substituted conjugated dienes and from to about 45 parts by weight of the polymerizable monomer; between about 0.4 and about 2.25 parts of sulfur, between about 0.05 and about 4 parts of 4-4 dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N-oxydiethylene-Z-benzothiazylsulfenamide and N-cyclohexyl-2-benzothiazylsulfenamide, based on 100 parts of saidrubber.

11. A rubber mix comprising a rubber selected from the group consisting of rubbery copolymers of vinyl- 'pyridines represented by the formula wherein R is selected from the group consisting of hydro gen, alkyl, vinyl and alpha-methyl vinyl groups, with at least one and not more than two of the groups being selected from the group consisting of vinyl and alphamethylvinyl, and the total number of carbon atoms in the alkyl groups being not greater than 12, with conjugated dienes containing 4 to 8 carbon atoms'per molecule and cyano and lower alkoxy substituted conjugated dienes; and rubbery terpolymers of said vinylpyridines with (1) said conjugated dienes and cyano and lower alkoxy substituted conjugated dienes and (2) polymerizable monomers selected from the group consisting of styrene, lower alkyl and alkoxy substituted styrenes, acrylonitrile, methacrylonitrile and lower alkyl acrylates and methacrylates; in which the monomer mixture from which the copolymers and terpolymers are prepared con tains from about 25 to about parts by weight of the vinylpyridine, from about 75 to about 95 parts by weight of the conjugated diene and cyano and lower alkoxy substituted conjugated dienes and from 0 to about 45 parts by weight of the polymerizable monomer; between about 0.4 and about 2.25 parts of sulfur, between about 0.05 and about 4 parts of 44' dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N-oxydiethylene-Z-benzo- 1 4 thiazylsulfenamide and N cyclohexylQ-benzothiazylsub f'enamide, based on 100 parts of said rubber.

12. A method for curing a rubber selected from the group consisting of rubbercopolymers of vinylpyridines represented by the formula R Rv where R is selected from the group consisting of hydro gen, alkyl, vinyl and alpha-methyl vinyl groups, with at least one and not more than two of the groups being selected from the group consisting of vinyl and alphamethylvinyl, and the total number of carbon atoms in the alkyl groups being not greater than 12, with conjugated dienes containing 4 to 8 carbon atoms per molecule and cyano and lower alkoxy substituted conjugated dienes; and

rubbery terpolymers of said vinylpyridines with (1) said conjugated dienes and cyano and lower alkoxy substituted conjugated dienes and (2) polymerizable monomers selected from the group consisting of styrene, lower alkyl and alkoxy substituted styrenes, acrylom'trile, methacrylonitrile and lower alkyl acrylates and methacrylates; in which the monomer mixture from which the copolymers and terpolymers are prepared contains from about 25 to about 5 parts by weight of the vinylpyridine, from about 75 to about parts byweight of-the conjugated diene and cyano and lower alkoxy substituted conjugated dienes and from 0 to about 45 parts by weight of the polymerizable monomer which comprises incorporating with said rubber between about 0.4 and about 225 parts of sulfur, between about 0.5 and about 4 parts of 4-4' dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N- oxydiethylene-2-benzothiazylsulfenamide and N-cyclohexyl-2-benzothiazylsulfenamide, based on parts of rubber and vulcanizing the rubber.

13. A vulcanized rubber prepared by incorporating into a terpolymer of acrylonitrile, butadiene and Z-methyl- S-vinylpyridine, prepared from a monomer mixture containing from about 25 to about 5 parts by weight of 2- methyl-S-vinylpyridine, from about-75 to about 95 parts by weight of butadiene and up to about 45 parts by weight of acrylonitrile, between about 0.4 and about 2.25 parts of sulfur, between about 0.5 and about 4 parts of 4-4' dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N-oxydiethylene-Z-benzothiazylsulfenamide and N-cyclohexyl-2benzothiazylsulfenamide, based on 100 parts of rubber and vulcanizing the rubber.

14. The vulcanized rubber of claim 13 in which the compound is N-oxydiethylene-Z-benzothiazylsulfenamide.

15. The vulcanized rubber of claim 13 in which the compound is N-cyclohexyl-Z-benzothiazylsulfenamide.

16. The method for curing a rubbery terpolymer of butadiene, acrylonitrile and 2-methyl-5-vinylpyridine prepared from a monomer mixture containing from about 75 to about 95 parts by weight of butadiene, up to about 45 parts by weight of acrylonitrile and from about 25 to about 5 parts by weight of Z-methyI-S-Vinylpyridine which comprises incorporating with said rubber between about 0.4 and about 2.25 parts of sulfur, between about 0.5 and about 4 parts of 4-4 dithiodimorpholine and between about 0.25 and about 2 parts of a compound selected from the group consisting of N-oxydiethylene-Z- benzothiazylsulfenamide and N-cyclohexyl-Z-benzothiazylsulfenamide, based .on 100 parts of rubber and vulcanizing the rubber.

17. The vulcanized rubber of claim 1 in which the rubbery copolymer is prepared from a monomer mixture which contains 75 parts of butadiene and 25 parts of 2- methyl-S-vinylpyridine.

18. The vulcanized rubber of claim 1 in which I 1? 16 References Cited in the file of this patent UNITED STATES PATENTS Barton Sept. 13, 1949 2,481,810 2,490,518 Hand Dec. 6, 1949 2,681,331 'Howland June 15, 1954 OTHER REFERENCES Rubber Chem. & Tech. 24, 211-223 (1951). (Copy in library.

10 Railsback et a1: Ind. and Eng. "Chem, vol. 49, No. 6,

pages 10434050, June 1957.

new, W 

1. A VULCANIZED RUBBER PREPARED BY INCORPORATING INTO A RUBBERY COPOLYMER OF BUTADIENE AND 2-METHYL-5-VINYLPYRIDINE PREPARED FROM A MONOMER MIXTURE CONTAINING FROM ABOUT 25 TO 5 PARTS OF 2-METHYL-5-VINYLPRIDINE AND FROM ABOUT 75 TO ABOUT 95 PARTS BYTADIENE, BETWEEN ABOUT 0.4 AND ABOUT 2.25 PARTS OF SULFUR, BETWEEN ABOUT 0.5 AND ABOUT 4 PARTS OF 4,4 DITHIODIMORPHOLINE AND BETWEEN ABOUT 0.25 AND ABOUT 2 PARTS OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF N-OXDIETHYLENE-2BENZETHIAZYSULFENAMIDE AND N-CYCLOHEXYL-2-BENZOTHIAZYLSULFENAMIDE, BASED ON 100 PARTS OF RUBBER AND VULCANIZING THE RUBBER. 